Process of producing rubber-like bodies



Patented May 29, 1928;

UNITED STATES 1,671,314 PATENT OFFICE.-

WILLIAM BEACH PRATT, OF WIlLLESLEY', MASSACHUSETTS, ASSIGNOR, BY HESNEAS- SIGNMENTS, TO vZDISIE'IECBISIONS PROCESS, INC., F DOVER, DELAWARE,A; COBPOB-Le TIOIN' OF DELAWARE.

PROCESS OF PRODUCING RUBBER-LIKE BODIES.

11o Drawing. Application filed February This invention has for itsobject the production of substitutes for natural crude rubber, such asobtained by the coagulation of the rubber globules contained, in thelatex I of He'vea brasz'liensis" and other so-called rubber trees.

'It has long been my theory that crude rubber consists of a mass ofadhering rubber globules, which preserve their identitiesnotwithstanding their adhesion to contiguous A globules, and in previousapplications for LettersPa'tent I have shown that by certain treatmentthe globules may be separated, ,one from another, and dispersed inwater. 15 It is furth generally agreed that the rubberglobule in latexcomprise a terpene center or core and a proteid protective envelope orfilm. Nature forms these globules in a serum of which the greater partis water, and on coagulation these separate globules become contractedand distorted in shape and form a coherent mass of-faciallycontactingand adhering particles or globules without' disrupting their protective26 films or coatings.

lnattempting to produce an equivalent rubber-like mass, it'would appearlogical at least to follow the order of production which naturehaspointed out. That is to say, it 30 has seemed to me that one shouldfirst produce what may be termed an aqueous disper- P sion of artificialglobules, each having a terpene center and a protective film or coating,and then cause the coagulation of such '36 globules in a coherent massof fa'cially adhering globules.

Since the center or core of naturally occurring globules is a terpene,one should select "-a terpene which approximates the 4 chemical andphysical characteristics thereof. Usually it is considered that thiscore or center is a polymerized mass of molecules of the-(C 11 group,but since there are a -17, me. Serial in. 88,988,

merization and of forming a sulphur addition'compound, as the logicalmaterial with which to work, the next step is to cause.

its polymerization and its [dispersion in water in globules of the sameorder of; ma nitude as naturally occurring rubber glo ules. which iswell known and need not be described in detail. But in efiecting thedispersion of theterpene in water, it is necessary to select somematerial which can be used to form the protective films or envelopes forthe dispersed globules. Such material should be hydrophilic or capableof water absorption, since this is a characteristic of the protective'envelo as or coatings of naturally occurring rubber globules. There arevarious proteids which may be employed, includin various animal orvegetable albumens, gFutens and even starches, when they have beenproperly treated.

I have found that it is possible to effect the dispersion of varioussubstances which are immiscible with water in larger than naturallyoccurring crude rubber globules, as pointed out in my application SerialNo. 749,803, filed November 13,

1924. To accomplish this the material must be formed into a sticky oradhesive or plastic mass at a temperature above the freezing oint andbelow the boiling point of water. This is done by either heating orchilling the material according to .its natural viscosity at roomtemperature. The terpene selectedpolymerized isoprene for example-according to one method of practising my invention, is placed in a two-blademixer of the general character of a Werner & Pfleiderer or dough mixerin which two helicoidal blades are slowly rotated at relativelydifferent speeds in a trough-like casing without touching or scrapingeach other or the internal walls of the'casing. Such a mixer eat manyspecies of crude rubber, I- think should be provided with a cover and ajacket 1t possible, and indeed have vreason for believing it probable,that the terpene centers of some of these naturally occurring globulesconsist o'Ldifierent groupings of carbon and hydrogen atoms. In allcases, however, where a vulcanizable crude rubber isformed,

theterp'ene center must be capable of adding,

on, sulphur by chemical reaction.- Consul.- ering isoprene; or evendipentene, orsome other equivalent terpene .capablefof polyj l' V I Thestep of, polymerization is one.

particle size no the protective coatings of rubber globules,nevertheless to the present date it has been found necessary to employ are-agent in order to treat the hydrophilic colloid to produce in it thedesired physical characteristics of strength and elasticity.

All crude rubbers have present in the mass, in addition to the rubberglobules, an amount of resinous material which aids in the adhesion ofglobule to globule, and which, without doubt, produces added strength tothe coagulated mass when used in the arts for the particular purposesdesired. The percentage of such resinous o-r extractable material inHevea rubber is from 3% to 5%. In lower grades of rubber thisextractable resinous content consists of from to 50% of the total mass.

I/Vhether this resinous material in the natural rubber is represented bythe breaking down of less stable globules of the rubber mass oncoagulation, or whether it is a free resin dispersed in the serum of thelatex, is not essential in considering the rubber-like inass I have beenable to produce. I may, if desired, in order to produce certain physicalmaterial extractable with acetone such as secured from true naturalrubbers, and the resulting globular structure formed by my process wouldbe retained as non-extractable material just as occurs from theextraction of natural rubbers.

What I claim is:

A process as herein described, which comprises dispersing a polymerizedterpene of the general type of (C H capable of reacting with sulphur, inparticles of colloidal size and coating such dispersed particles withhydrophilic proteid films or envelopes, tanning the films or envelopesof the dis persed particles to increase the strength and toughnessthereof, coagulating the particles, and separating and drying thecoagulated mass of individual globules or particles.

In testimony whereof I have afiixed my signature.

WILLIAM BEACH PRATT.

